Distribution Apparatus and Playback Apparatus

ABSTRACT

A distribution apparatus has an input section  200  for receiving video or audio transmission data; a storage section  201  for storing the transmission data received by the input section  200  as playback data; a distribution request reception section  203  for accepting a distribution request message including information for designating a distribution range of the playback data from the playback apparatus  102 ; and a distribution section  204  for inserting data corresponding to the distribution range among the playback data stored in the storage section  201  into a response message to the distribution request message, and for distributing the data to the playback apparatus  102  originating the distribution request.

TECHNICAL FIELD

The present invention relates to a distribution apparatus for receivingtransmission data of video, audio and the like and for storing them asplayback data, and to a playback apparatus for receiving the playbackdata distributed from the distribution apparatus and for playing backthe data to the video, audio and the like.

BACKGROUND ART

In recent years, it has become common practice to record television(abbreviated as TV from now on) broadcasts on random access storagemedia such as DVDs (Digital Versatile Disks) and hard disks. PatentDocument 1 and Patent Document 2 describe time-shift playback ofrecorded contents using a random access storage medium.

In a random access storage medium, it is possible to designate anaddress for storing a broadcasting program and an address for playingback the program contents individually. Therefore even during recordinga broadcasting program, as for program contents already recorded,special playback such as fast playback, partly cut video playback,rewinding playback, slow-motion playback, and time-shift playback ispossible by manipulating the proceeding speed or proceeding direction ofthe playback address.

Patent Document 1: Japanese Patent Laid-Open No. 7-264529/1995; and

Patent Document 2: Japanese Patent Laid-Open No. 2000-350130.

For example, to perform special playback such as time-shift playbackduring recording of a broadcasting program into a storage device, it isnecessary for a playback section to set an extent of the programcontents that have already been stored in the storage device and areready for playback to prevent an error from occurring during theplayback.

On the other hand, the time-shift playback is possible by connecting,for example, distribution apparatuses with a function of receiving andstoring one or both of the video data and audio data of a broadcastingprogram with a playback apparatus with a function of playing back thedata about the broadcasting program stored in the distributionapparatuses via a communication network that enables mutual datacommunications, and by enabling a single playback apparatus to receivethe data about the broadcasting program stored and distributed by theplurality of distribution apparatuses on the communication network.

In this system configuration, it is also necessary as described abovethat the extent of the program contents, which have already been storedin the distribution apparatus and are ready for distribution to theplayback apparatus, is set in the playback apparatus. To achieve this,communication is carried out between the playback apparatus and thedistribution apparatus via the communication network for notifying ofthe extent of the program contents that can be distributed.

The foregoing communication, however, takes time to process acommunications protocol generated anew and to transmit the information.Thus, when the distribution apparatus records the video data and audiodata and distributes them via the communication network, and theplayback apparatus plays back them, a problem arises of damagingreal-time property between the video data and audio data stored in thedistribution apparatus and the video and audio played back by theplayback apparatus.

The present invention is implemented to solve the foregoing problem.Therefore it is an object of the present invention to provide adistribution apparatus and a playback apparatus capable of reducingcommunication volume and communication duration for notifying of theextent of the data that can be distributed at the playback that iscarried out by distributing video data, audio data and the like via acommunication network with storing these data, for example.

DISCLOSURE OF THE INVENTION

A distribution apparatus in accordance with the present inventionincludes: an input section for receiving transmission data; a storagesection for storing the transmission data received by the input sectionas playback data; a distribution request reception section for acceptingfrom a playback apparatus a distribution request message includinginformation for designating a distribution range of the playback datavia a communication network; and a distribution section for distributingdata corresponding to the distribution range among the playback datastored in the storage section to the playback apparatus originating adistribution request via the communication network with inserting thedata into a response message to the distribution request message. Withsuch a configuration, it offers an advantage of being able to reduce thecommunication volume and communication duration for notifying of thedistributable data range at the time of storing the transmission datasuch as video data and audio data into the storage section anddistributing the data via the communication network to be played back.This makes it possible to suppress the damage of the real-time propertybetween the data being stored and the contents played back even in thecase where the transmission data such as video data and audio data arebeing stored to be played back via the communication network.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a configuration of a network systemincluding a distribution apparatus and a playback apparatus of anembodiment 1 in accordance with the present invention;

FIG. 2 is a block diagram schematically showing a configuration of thedistribution apparatus in FIG. 1;

FIG. 3 is a block diagram schematically showing a configuration of theplayback apparatus in FIG. 1; and

FIG. 4 is a block diagram schematically showing a configuration of theplayback apparatus of an embodiment 2 in accordance with the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

The best mode for carrying out the invention will now be described withreference to the accompanying drawings to explain the present inventionin more detail.

Embodiment 1

FIG. 1 is a diagram showing a configuration of a network systemincluding a distribution apparatus and a playback apparatus of anembodiment 1 in accordance with the present invention. To a network(communication network) 100, distribution apparatuses 101 and playbackapparatuses 102 are connected. As for the network 100, it can be a wireor wireless network regardless of its physical form. In addition, aslong as the apparatuses are in a state capable of carrying outcommunication according to a specified protocol such as TCP/IP(Transmission Control Protocol/Internet Protocol), they are consideredto be connected to the network 100.

It is assumed in the embodiment 1 that at least one distributionapparatus 101 and one playback apparatus 102 are connected to thenetwork 100 although their numbers are not specified. The distributionapparatuses 101 receive content data (transmission data) of TVbroadcasting, radio broadcasting, video distribution or musicdistribution via the Internet, and store the content data in theirinternal storage sections.

In addition, the distribution apparatuses 101 distribute via the network100 the contents requested to distribute from among the stored contentdata (playback data) by the playback apparatus 102. The distributionapparatuses 101 are embodied by applying the present invention torecording playback apparatuses of TV broadcasts and the like, which areable to communicate with the playback apparatuses 102 via the network100, for example. Besides, as the distribution apparatuses 101, such anapparatus is also possible which has, in addition to the recordingplayback apparatus including a hard disk drive for recording TVbroadcasting programs, a memory for temporarily storing the receivedcontent data for several seconds to several minutes, for example, anddistributes the data stored in the memory immediately.

The playback apparatuses 102 request the distribution apparatuses 101 todistribute contents, and play back the content data the distributionapparatuses 101 distribute with receiving them. The playback apparatuses102 are embodied in a mobile phone or a mobile communication terminalconnected to the network 100 via radio communications as shown inFIG. 1. Besides, such a case is also conceivable in which they areconfigured as an information communication terminal that is connected tothe network 100 via communication through wire, receives and plays backthe content data distributed from the distribution apparatus 101, anddisplays on a monitor 103.

Incidentally, the term “contents” in the present invention refers to atleast one of video and audio information. In addition, the term “contentdata”, which means transmission data received by the distributionapparatuses 101, refers to at least one of the video data that can beplayed back to images by the playback apparatuses 102 and the audio datathat can be played back to voices. As for a protocol used fordistribution requests for the contents from the playback apparatuses 102and used for the content distribution by the distribution apparatuses101, HTTP (HyperText Transfer Protocol) is employed, for example.

In this case, the contents stored in the distribution apparatus 101 anddistribution apparatus 101 are identified by URI (Uniform ResourceIdentifiers). Accordingly, the playback apparatuses 102 make aconnection with the distribution apparatus 101 designated by URI usingTCP/IP, and request for the contents designated by URI according to anHTTP request message.

In the case of making a partial distribution request for the contents,the playback apparatuses 102 add to the HTTP request message an HTTPrange header for designating the range of the distribution requestcontents or a header the distribution apparatus 101 can recognize.

The playback apparatuses 102 can assign the distribution request rangeof the contents to the distribution apparatus 101 by insertinginformation about the range of the contents requested to be distributedinto the header added to the HTTP request message, and by transmittingit to the distribution apparatus 101. The header described above isreferred to as a “distribution range designating header” from now on.The distribution range designating header, for example, can specify thecontent range from 500 seconds to 600 seconds by setting as “Time-Range:time=500-600”.

When requesting notification of the range of the contents which havealready been stored in the distribution apparatuses 101 and areavailable for distribution, the playback apparatuses 102 add the headerthe distribution apparatuses 101 can recognize to the transmission datato the distribution apparatuses 101, thereby notifying them of therange. For example, the header for requesting the notification of thedistributable content range is named “Request-Current-Range”, and thevalue of the header is set at “TRUE”. Such a header is referred to as a“distributable range request header” from now on.

For the content distribution request from the playback apparatuses 102,the distribution apparatuses 101 transmit the distribution request rangeof the contents requested to be distributed by using an HTTP responsemessage. In this case, if the notification of the distributable contentrange is requested using the distributable range request header asdescribed above, for example, the distribution apparatuses 101 insertthe information for notifying of the distributable content range intothe header added to the HTTP response message, and transmit to theplayback apparatuses 102.

For example, assume that the header for notifying of the distributablecontent range is named “current-range”, and the value of the header isset at “byte=start position-end position” to represent the startposition and end position of the distributable contents which havealready been stored in units of bytes. Alternatively, the value of theheader is set at “time=start position-end position” to represent thestart position and end position of the distributable content data whichhave already been stored in units of time such as hours, minutes, andseconds. Such a header is referred to as a “distributable rangenotification header” from now on.

Although the present embodiment 1 is described under the assumption thatit employs HTTP as the protocol for transmitting the content data, anyprotocols other than HTTP are also available as long as they enable thedistribution request for the specified range of the contents andexpansion of the header portion. In addition, although the presentembodiment 1 is described under the assumption that it employs URI foridentifying the contents, using identifying methods other than URI isalso possible as long as the distribution apparatus 101 and distributionapparatus 101 can identify the distributable contents.

Next, the operation of the distribution apparatus 101 will be described.

FIG. 2 is a block diagram schematically showing a configuration of thedistribution apparatus of FIG. 1, with reference to which the operationof the distribution apparatus 101 will be described. In FIG. 2, blocksequivalent in their functions to the blocks in the network configurationas shown FIG. 1 are designated by the same reference numerals and theirdescription will be omitted.

An input section 200 is a section for receiving the content dataconsisting of a specific program acquired from broadcasting such as TVbroadcasting, and for storing the content data in a storage section 201.The input section 200 can be embodied in a section which enables areceiving apparatus such as a tuner for receiving the TV broadcastingand software for controlling its operation or signal processing tooperate in corporation. A configuration is also possible which receivesthe content data from radio broadcasting, or from video distribution ormusic distribution via the Internet besides the TV broadcasting.

In addition, the input section 200 successively stores the contents intothe storage section 201 with receiving the content data. In this case,the input section 200 records in storage management information 202 aposition on the contents represented in units of bytes and a storedlocation in the storage section 201 represented in units of bytes as therange of the contents stored in the storage section 201. For example,the content data, as to which the stored contents are defined from thestart position to the end position in units of bytes, and the individualstored locations in the storage section 201, at which the content dataare stored and which are defined in units of bytes, are stored withestablishing correspondence between them.

Furthermore, concerning the contents in the range stored in the storagesection 201, the input section 200 prepares a correspondence tablebetween the time on the contents and the stored locations on the storagesection 201, and adds the table to the storage management information202. For example, it defines the stored contents from the start point oftime to the end point of time in units of time, and stores thecorrespondence table that establishes correspondence between theindividual time and the stored locations in the storage section 201 atwhich the data corresponding to the contents at the individual time arestored.

Here, the storage management information 202 is information for managingthe contents stored in the storage section 201. The input section 200can write information about the contents into the storage managementinformation 202 or erase the information therefrom, and a distributionsection 204 can refer to its contents. The storage managementinformation 202 can be arranged on the storage section 201, for example.

When the contents are erased from the storage section 201, the inputsection 200 deletes from the storage management information 202 theforegoing correspondence table about the contents in the range erased.The deleting processing of the correspondence table enables only therange of the contents stored in the storage section 201 to have thecorrespondence table in the storage management information 202. Such acorrespondence table is referred to as “time-position correspondencetable” from now on.

In this way, the storage management information 202 for specifying thestored location of the contents in units of time and in units of bytesare stored in the storage section 201. Thus, regardless of whether theunit for designating a particular range of the contents is byte or time,referring to the storage management information 202 makes it possible todetermine the storage area in the storage section 201 in which theparticular range of the contents are stored.

The time-position correspondence table is a table that arranges, for theentire time information or for part of the time information in thecontents, the combination of the time information embedded in thecontent data and the stored location in the storage section 201 at whichthe front portion of the data structure containing the time informationis stored.

For example, when the content data stream is MPEG-2TS, the values of thetime information PCR (Program Clock Reference) included in the contentsare read; and for all or part of the PCR, the combinations are arrangedof the PCR and the stored locations in the storage section 201 at whichthe first one byte of each transport stream packet, the data structureincluding the PCR, is stored.

Here, the unit of the PCR can be converted to time units such as hours,minutes, and seconds. By thus doing, as for any arbitrary time,searching for the PCR indicating the closest time to it from thetime-position correspondence table, and reading the stored location inthe storage section 201 that makes a group with the PCR make it possibleto specify the stored location in the storage section 201 at which thecontent data corresponding to the time is stored.

Here, the playback apparatus 102 can play back the contents more easilyby placing the stored location in the storage section 201, which is tobe combined with the time information, at the top of the data structureconstituting the units of the playback processing. For example, when thecontent data stream is MPEG-2TS, the time-position correspondence tableis arranged from the combinations of the PCR and the stored locations inthe storage section 201 at which the values of the front portions of theGOPs (Groups Of Pictures), drawing units in the playback processing, arestored, rather than the values of the front portions of the transportstream packets described above.

In addition, although the example of arranging the time-positioncorrespondence table using the PCR as the time information is shownabove, one of the PTS (Presentation Time Stamp) and DTS (Decoding TimeStamp), which are the time information contained in the MPEG-2 stream,can also be used. For example, the input section 200 reads the values ofthe PTS (or DTS) included in the contents, and arranges for all or partof the PTS (or DTS) the combinations of the PTS (or DTS) and the storedlocations in the storage section 201 at which the first one byte of eachtransport stream packet, the data structure including the PTS (or DTS),is stored. Then, as for any arbitrary time, searching for the PTS (orDTS) indicating the closest time to it from the time-positioncorrespondence table, and reading the stored location in the storagesection 201 that makes a group with the PTS (or DTS) make it possible tospecify the stored location in the storage section 201 at which thecontent data corresponding to the time is stored.

The storage section 201 is a section for storing the content datareceived by the input section 200 regardless of whether storingtemporarily or semi-permanently. For example, in addition to thesemipermanent storage such as recording broadcasting programs and thelike, such a case is conceivable which stores temporarily for severalseconds to several minutes. Furthermore, a memory such as a DRAM or SRAMcan also be used as the storage section 201 to form a ring buffer. Tosuccessively store the content data in the storage section 201, thecontent data can overwrite the content range already stored. Inaddition, using a large-capacity hard disk as the storage section 201will make it possible to store the content data within the limit of thecapacity.

A distribution request reception section 203 accepts an HTTP requestmessage which is a content distribution request from the playbackapparatus 102, and asks the distribution section 204 for thedistribution of the contents corresponding to the HTTP request message.More specifically, the distribution request reception section 203,receiving the HTTP request message from the playback apparatus 102,notifies the input section 200 to receive the content data requested tobe distributed by the HTTP request message, and to store the contentdata in the storage section 201.

According to the notification, as described before, the input section200, receiving the content data requested to be distributed,successively stores the content data in the storage section 201, andrecords in the storage management information 202 the positions on thecontents represented in units of bytes, and the stored locations on thestorage section 201 represented in units of bytes as the range of thestored contents. Furthermore, as for the contents within the rangestored in the storage section 201, the input section 200 prepares thecorrespondence table between the time on the contents and the storedlocations on the storage section 201, and adds the table to the storagemanagement information 202.

Next, the distribution request reception section 203 reads the range ofthe contents designated by the distribution range designating header ofthe HTTP request message received, and notifies the distribution section204 of the range. In addition, when the HTTP request message receivedfrom the playback apparatus 102 includes the distributable range requestheader, the distribution request reception section 203 notifies thedistribution section 204 to transmit the distributable rangenotification header to the playback apparatus 102.

The distribution section 204 reads from the storage section 201 thecontent data within the range notified by the distribution requestreception section 203, places the content data on the HTTP responsemessage, and distributes them to the playback apparatus 102. In thiscase, the distribution section 204 determines the location where thecontent data within the notified range is stored in the storage section201 by referring to the storage management information 202.

Furthermore, the distribution section 204 does not distribute thecontents in the range the storage section 201 does not store. Thus, tonotify the playback apparatus 102 of the actually distributed range ofthe contents, the distribution section 204 adds to the HTTP responsemessage a notification header of the distribution range which carriesthe information about the content range, and transmits the notificationheader to the playback apparatus 102. Such a header is referred to as a“distribution range notification header” from now on.

The case will be described where the distribution request receptionsection 203 notifies the distribution section 204 to transmit thedistributable range notification header to the playback apparatus 102.In this case, when the distribution section 204 places the content dataon the HTTP response message and distributes them to the playbackapparatus 102, it refers to the storage management information 202,reads the information about the range of the contents stored in thestorage section 201, sets it in the distributable range notificationheader, and places the header on the HTTP response message. Here, theterm “information about the range of the contents” refers to theinformation that defines the content data from beginning to end of thecontents stored in the storage section 201 in units of time or bytes.

Next, the operation of the playback apparatus 102 will be described.

FIG. 3 is a block diagram schematically showing a configuration of theplayback apparatus of FIG. 1, with reference to which the operation ofthe playback apparatus will be described. In FIG. 3, the componentshaving functions equivalent to the components of the networkconfiguration shown in FIG. 1 are designated by the same referencenumerals, and their duplicate description will be omitted.

A selecting section 300 is a section for a user of the playbackapparatus 102 to set and input playback conditions such as contents tobe played back and a playback start position. The selecting section 300is embodied in a section that enables a display unit not shown, asetting and inputting device using key input or the like, and softwarefor controlling signal processing by using these devices to operate incooperation.

In addition, the selecting section 300 maintains the metadata on thecontents, and shows the user a list of the metadata on the contentsthrough a GUI (Graphical User Interface) or the like so that the usercan decide the contents to be played back and the playback startposition. It is assumed here that the metadata on the contents of thepresent embodiment 1 includes the URI of the contents.

When the URI of the content data is selected as the information forspecifying the contents to be played back, the selecting section 300notifies a distribution request section 301 of the URI of the contentdata selected. In addition, when the playback start position of thecontent data selected is selected, the selecting section 300 writes theplayback start position of the contents in position information 304.

Using HTTP, the distribution request section 301 transmits an HTTPrequest message for requesting to distribute the content data designatedby the URI to the distribution apparatus 101 designated by the URInotified by the selecting section 300. In this case, the distributablerange request header is included in the HTTP request message. Inaddition, the range of the contents requested to be distributed isassumed to be designated by a control section 305. As for the unit inthis case, it is assumed to be the unit employed by the control section305 to designate the range.

According to HTTP, a receiving section 302 receives the HTTP responsemessage including the distribution range notification header and contentdata from the distribution apparatus 101 via the network 100. Inaddition, when having transmitted the distributable range request, thereceiving section 302 receives, according to HTTP, the HTTP responsemessage including the distributable range notification header andcontent data from the distribution apparatus 101.

Receiving the distribution range notification header in the HTTPresponse message, the receiving section 302 notifies the control section305 of the information about the content range informed by thedistribution range notification header. Furthermore, receiving thedistributable range notification header, the receiving section 302notifies the control section 305 of the information about thedistributable range informed by the distributable range notificationheader. In addition, the content data received via the HTTP responsemessage is supplied from the receiving section 302 to a playback section303 to be played back successively.

The position information 304 records the position on the contents inunits of bytes and in units of time. The position information 304 makesit possible in the case of motion video contents, for example, tospecify the video contents corresponding to the position on the motionvideo determined in units of playback time, and to specify the videocontents corresponding to the position on the motion video in units ofplayback information volume (in units of bytes). The positioninformation 304 allows the information about the contents selected bythe selecting section 300 to be written, and the control section 305 canrefer to the contents. The information is stored in a storage sectionnot shown which is accessible by the selecting section 300 and controlsection 305, for example.

The control section 305 notifies the distribution request section 301 tomake a request to the distribution apparatus 101 to distribute thecontents within a prescribed range from the position on the contentsspecified by referring to the position information 304. As the unit ofthe range of the contents to be sent to the distribution request section301, the unit of the position on the contents recorded in the positioninformation 304 is used.

If the receiving section 302 notifies it of the distributable range, thecontrol section 305 limits the range of the contents requested to bedistributed by the distributable range. As the range of the contentsrequested to be distributed, even the entire contents are allowed, forexample. If the content data is MPEG-2 encoded data, the range can bethe length of GOP or the length including a piece of picture.

As for a method of limiting the range of the contents requested to bedistributed by the distributable range, it limits to the range common tothe range of the contents requested to be distributed and thedistributable range. In this case, unless the common range is present,this can be made an error, or the distributable range itself can be setas the range of the contents requested to be distributed.

Furthermore, the control section 305 updates the contents of theposition information 304 by overwriting the contents with the end valueof the distribution range notified by the receiving section 302. The endvalue becomes the start value of the contents at the time whendesignating the distribution range continuously. Unless the distributionrange is notified by the receiving section 302, the control section 305updates the contents of position information 304 by the end value of therange of the contents requested to be distributed informed to thedistribution request section 301.

As described above, according to the present embodiment 1, the playbackapparatus 102 inserts the distribution range designating header into theHTTP request message for requesting the distribution of the contents,and transmits it to the distribution apparatus 101 via the network 100.The distribution apparatus 101 inserts the data within the rangespecified by the distribution range designating header among the contentdata stored in the storage section 201 into the HTTP response message,and distributes to the playback apparatus 102 that originates thedistribution request via the network 100. Thus inserting the contentdata and the information about the designation of the distribution rangeinto the HTTP request message and into the response message to it canprevent new communications other than the communications required forthe distribution request and distribution of the contents from occurringbetween the distribution apparatus 101 and the playback apparatus 102.Accordingly, even if the contents are played back via the network whilestoring them in the storage section 201, the present embodiment 1 cansuppress the occurrence of a factor that will damage the real-timeproperty between the stored contents and the played back contents. Thisenables streaming playback of video and audio live contents, forexample.

Embodiment 2

The present embodiment 2 corrects the range of the contents requested tobe distributed considering the delay from the time the playbackapparatus transmits the distribution request of the contents to thedistribution apparatus to the time it receives the content data.

FIG. 4 is a block diagram schematically showing a configuration of theplayback apparatus of the embodiment 2 in accordance with the presentinvention. In FIG. 4, the components with the functions equivalent tothe components shown in FIG. 3 are designated by the same referencenumerals, and their duplicate description will be omitted. Going-aroundtime information 400 is information that represents in units of time theduration from the time when the control section 402 notifies thedistribution request section 301 of making a content distributionrequest to the time when the receiving section 302 actually receives thecontent data.

In addition, the going-around time information 400 is information intowhich a timer 401 can write time information, and the contents of whichthe control section 402 can refer to. The going-around time information400 is stored in a storage section not shown provided in the playbackapparatus 102, for example. As for the timer 401, the control section402 controls the start and stop of its time measurement. The timer 401measures the duration from the time when the control section 402notifies the distribution request section 301 of the contentdistribution request to the time when the receiving section 302 receivesthe content data, and records measurement results as the going-aroundtime information 400.

The control section 402 has the functions similar to the functions ofthe control section 305 of FIG. 1 described in the foregoingembodiment 1. The control section 402 differs from the control section305 in FIG. 1 in the operation that according to the going-around timeinformation 400 it corrects errors of the distributable range resultingfrom the transmission delay in the network 100, from the delay due toprocessing in the distribution apparatus 101, and from the delay due toprocessing by the playback apparatus 102 itself.

Next, the operation will be described.

It will be explained with reference to FIG. 4 in addition to FIG. 1described in the foregoing embodiment 1.

First, when notifying the distribution request section 301 of thedistribution request for the contents, the control section 402 carriesout the start control of the time measurement by the timer 401. Thus,the timer 401 starts the time measurement from the time when the controlsection 402 notifies the distribution request section 301 of the requestfor the distributable range of the contents.

In addition, as in the foregoing embodiment 1, when making thedistributable range request to the distribution apparatus 101, thereceiving section 302 receives, according to HTTP, the HTTP responsemessage including the distributable range notification header andcontent data from the distribution apparatus 101. In this case, thereceiving section 302 notifies the control section 402 of theinformation about the distributable range notified via the distributablenotification header.

Notified by the receiving section 302 of the distributable range, thecontrol section 402 carries out the end control of the time measurementby the timer 401. Thus, the timer 401 measures the duration from thetime when the control section 402 notifies the distribution requestsection 301 of making the distribution request for the contents to thedistribution apparatus 101 to the time when the content data is receivedvia the HTTP response message. The timer 401 records the measurementresult in the going-around time information 400.

Referring to the time recorded in the going-around time information 400,the control section 402 adds the time to the start time of thedistributable range notified by the receiving section 302 as correctingtime. This makes it possible to correct the errors of the distributablerange resulting from the transmission delay in the network 100, from thedelay due to processing in the distribution apparatus 101, and from thedelay due to processing by the playback apparatus 102 and the like.

After that, the control section 402 notifies the distribution requestsection 301 to request the distribution apparatus 101 to distribute thecontents within the distributable range corrected as described abovefrom the position on the contents recorded in the position information304.

According to the notification, the distribution request section 301,using the HTTP, transmits an HTTP request message for requesting todistribute the content data designated by the URI to the distributionapparatus 101 designated by the URI notified by the selecting section300. In this case, the distributable range corrected by the controlsection 402 as described above is set in the distribution rangedesignating header to be included in the HTTP request message.

The distribution apparatus 101, which receives the HTTP request messagefrom the playback apparatus 102, operates in the same manner as in theforegoing embodiment 1, and distributes the contents in accordance withthe distributable range corrected. In this way, the playback apparatus102 can playback the contents in the playback conditions whose errorsdue to the foregoing delays are corrected. For example, when thedistribution apparatus 101 distributes the content data while storingit, the playback apparatus 102 can play back the contents withoutdamaging the real-time property between its contents and the contentsstored in the distribution apparatus 101.

As described above, according to the present embodiment 2, the playbackapparatus 102 corrects the transmission delay in the network 100, thedelay due to the processing in the distribution apparatus 101, and thedelay due to the processing by the playback apparatus 102, which areincluded in the distributable range notified by the distributionapparatus 101. This makes it possible to suppress the distributionrequest for the contents out of the range the distribution apparatus 101can distribute, thereby being able to reduce a useless communicationvolume.

Embodiment 3

The configuration of the playback apparatus of the present embodiment 3is basically the same as that of FIG. 3 shown in the foregoingembodiment 1 and that of FIG. 4 shown in the foregoing embodiment 2. Itdiffers from the configurations of the foregoing embodiments in that thecontrol section carries out the processing for the special playback atthe time of updating the position information that stores the positionon the contents.

More specifically, as additional functions of the control section 305shown in FIG. 3 in the foregoing embodiment 1, and of the controlsection 402 shown in FIG. 4 in the foregoing embodiment 2, the controlsection of the present embodiment updates the position information 304using the value obtained by adding a prescribed offset value to the endvalue of the distribution range notified by the receiving section 302,or using the value obtained by subtracting a prescribed offset valuefrom the start value of the distribution range notified by the receivingsection 302. Alternatively, without adding or subtracting the offsetvalue, it can insert a delay into the range of the contents requested tobe distributed before notifying the distribution request section 301 tomake a distribution request.

For example, in the case where the content data is encoded dataaccording to MPEG, and when the control section updates the contents ofthe position information 304, the control section makes the length ofthe content range to be informed to the distribution request section 301equal to the length of the GOP, and updates them by making the offset tobe added to the end value of the distribution range notified by thereceiving section 302 equal to the length of the GOP subsequent to theforegoing GOP. Thus, 2× playback is achieved. On the contrary, bysubtracting the length equal to two GOPs from the start value of thedistribution range notified by the receiving section 302, −2× isachieved.

In addition, by making the content range to be informed to thedistribution request section 301 equal to the length of the GOP, bymaking the offset equal to zero, and by inserting the delay of timecorresponding to the length of the foregoing GOP, ½× is achieved. On thecontrary, −½× is achieved by making the content range to be informed tothe distribution request section 301, the offset, and the length of thedelay equal to the length of the GOP. In this case, as for the length ofthe offset, it need not be equal to the length of the GOP, but can beset at the length of an MPEG picture, or at a range from several secondsto several hours.

As described above, according to the present embodiment 3, the controlsection of the playback apparatus provides the offset corresponding tothe playback speed or inserts the delay at the time of updating thevalue of the position information 304 in accordance with the contents ofthe special playback. Thus, in response to this and according to thedata distributed by the distribution apparatus 101, the playback section303 can carry out fast playback and rewinding playback, andframe-by-frame playback and reverse frame-by-frame playback.

INDUSTRIAL APPLICABILITY

As described above, in the case where the distribution apparatus inaccordance with the present invention stores video data or audio dataand distributes the data via the network, and the playback apparatusplays back the data, the distribution apparatus can reduce thecommunication volume and communication duration for notifying theplayback apparatus of the distributable data range. Thus, thedistribution apparatus is suitable for a system for carrying outstreaming playback of video or audio live contents.

1. A distribution apparatus for distributing playback data to a playbackapparatus via a communication network, said distribution apparatuscomprising: an input section for receiving transmission data; a storagesection for storing the transmission data received by said input sectionas the playback data; a distribution request reception section foraccepting from said playback apparatus a distribution request messageincluding information for designating a distribution range of theplayback data via said communication network; and a distribution sectionfor distributing data corresponding to the distribution range among theplayback data stored in said storage section to the playback apparatusoriginating a distribution request via said communication network withinserting the data into a response message to the distribution requestmessage.
 2. The distribution apparatus according to claim 1, whereinsaid distribution section, when the distribution request message fromsaid playback apparatus includes information for requesting to notify ofa range of the playback data already stored in said storage section,inserts, in accordance with the information, information for notifyingof the range of the playback data stored in said storage section intothe response message, and distributes to said playback apparatusoriginating the distribution request.
 3. The distribution apparatusaccording to claim 1, wherein said storage section stores informationthat defines the stored playback data in at least one of units of timeand units of information volumes and a stored location at which theplayback data specified by the information is stored with establishingcorrespondence between the information and the stored location; and saiddistribution section specifies in said storage section the playback datacorresponding to the information for designating the distribution rangeincluded in the distribution request message according to thecorrespondence in said storage section.
 4. The distribution apparatusaccording to claim 1, wherein the playback data is MPEG encoded data;said storage section stores one of PCR (Program Clock Reference), PTS(Presentation Time Stamp) and DTS (Decoding Time Stamp), which are timeinformation included in the stored playback data, and a stored locationat which a top value of GOP (Group Of Pictures) of the playback datacorresponding to the time specified by the time information is stored,with establishing correspondence between one of the PCR, PTS and DTS andthe stored location; and said distribution section specifies in saidstorage section the playback data corresponding to the information fordesignating the distribution range included in the distribution requestmessage according to the correspondence in said storage section.
 5. Aplayback apparatus for receiving and playing back playback datadistributed from a distribution apparatus via a communication network,said distribution apparatus receiving transmission data and storing thetransmission data as the playback data, said playback apparatuscomprising: a distribution request section for inserting information fordesignating a distribution range into a distribution request message forthe playback data, and for transmitting the distribution request messageto said distribution apparatus via said communication network; areceiving section for receiving a response message that is distributedfrom said distribution apparatus in response to the distribution requestmessage, and that includes data corresponding to the distribution rangeamong the playback data stored by said distribution apparatus; aplayback section for playing back the playback data received by saidreceiving section to original contents; and a control section forcontrolling the distribution request from said distribution requestsection to said distribution apparatus.
 6. The playback apparatusaccording to claim 5, wherein said control section, when the responsemessage includes information for notifying of a range of the playbackdata distributable among the data stored in said distribution apparatus,generates, within a range specified by the information, information fordesignating a range requested to be distributed, and sets theinformation in said distribution request section; and said distributionrequest section generates a distribution request message including theinformation for designating the distribution range set by said controlsection, and transmits the distribution request message to saiddistribution apparatus.
 7. The playback apparatus according to claim 5,wherein said control section specifies a range of the playback datarequested to be distributed in accordance with information that definesthe stored playback data in at least one of units of time and units ofinformation volumes, generates the information for designating thedistribution range, and sets the information in said distributionrequest section.
 8. The playback apparatus according to claim 5, whereinsaid control section corrects the information for designating thedistribution range using time elapsed from instructing said distributionrequest section about the distribution request to receiving the playbackdata distributed by said distribution apparatus.
 9. The playbackapparatus according to claim 7, wherein said control section alters,according to contents of special playback, contents of the informationthat defines the playback data in at least one of units of time andunits of information volumes, or contents of the information fordesignating the distribution range; and said playback section carriesout, in accordance with the information altered by said control section,the special playback corresponding to the alteration as to the playbackdata distributed from said distribution apparatus.